cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
416
Views
0
Helpful
2
Replies

CEF and Fast switching on same int

jamey
Level 4
Level 4

How does this work if both CEF and Fast switching are both enabled on the same interface? How does it know to use CEF?

sh ip int:

FastEthernetx/x is up, line protocol is up

IP fast switching is enabled

IP fast switching on the same interface is disabled

IP Flow switching is disabled

IP CEF switching is enabled

IP Feature Fast switching turbo vector

IP Feature CEF switching turbo vector

IP multicast fast switching is disabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast, CEF

-TIA

1 Accepted Solution

Accepted Solutions

ruwhite
Level 7
Level 7

CEF will attempt to switch the packet first, and if it cannot, it will "punt" the packet to the next slower switching path, in this case fast switching. It's just the way the code is written--the switching vector associated with an interface is a list of sorts, and hardware is always first on that list, followed by CEF, then followed by fast, and then other methods....

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6c9.html

Look for punt.

:-)

Russ.W

View solution in original post

2 Replies 2

Harold Ritter
Cisco Employee
Cisco Employee

CEF is the primary switching path when enabled on an interface.

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

ruwhite
Level 7
Level 7

CEF will attempt to switch the packet first, and if it cannot, it will "punt" the packet to the next slower switching path, in this case fast switching. It's just the way the code is written--the switching vector associated with an interface is a list of sorts, and hardware is always first on that list, followed by CEF, then followed by fast, and then other methods....

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6c9.html

Look for punt.

:-)

Russ.W

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: